Cell Core Facility Mesenchymal Stem Cells (MSCs) are an important cellular component of the bone marrow microenvironment as progenitor cells of multiple mesenchymal phenotypes including osteoblasts, chondrocytes, adipocytes and marrow stromal fibroblasts and potentially other mesenchymal phenotypes (Figure 1). MSCs make a large array of cytokines, prostaglandins, extracellular matrix molecules and cell surface receptors and have been reported to support the differentiation and expansion of hematopoietic progenitors in vitro. The Cell Core will serve as a centralized technical and dispensing facility, dedicated to producing MSCs using Standard Operating Procedures (SOPs) to insure that the research projects will be conducted with the same high quality MSC preparations. In addition, the Cell Core Facility will conduct quality control assays including the screening, selection and procurement of specialized reagents needed for the isolation and expansion procedures. In particular, the fetal bovine serum used in the culture-expansion medium must be carefully screened and selected. Finally, the Cell Core Facility will conduct experimentation to optimize the chondrogenic potential of the cell preparations to be supplied to the Program Investigators. These experiments will be designed to validate preliminary data obtained with human MSCs. The services to be provided by the Cell Core Facility are summarized by the following specific aims. SpecificAim 1: To provide high quality Mesenchymal Stem Cell (MSC) and chondrocyte cultures, customized to the needs of each Research Project, in a timely and cost-effective manner. Specific Aim 2: To optimize animal cell preparations and culture systems for chondrogenesis. Specific Aim 2a: To assess the effect of FGF-2 supplementation during mitotic expansion on the chondrogenic potential of rabbit MSCs and chondrocytes Specific Aim 2b: To study the role of TGF-p1 in the regulation of hypertrophic differentiation of rabbit MSCs and chondrocytes. It is important to stress here, that while parts of this document focus on human MSCs (hMSCs), the contribution of this Core to the overall Research Program is to deliver rabbit bone marrow-derived MSCs and rabbit chondrocytes from different anatomical locations to grant participants and collaborators and to develop optimized culture conditions for expansion and chondrogenic differentiation of these cells. The standard operating protocols and procedures (SOPs) for these preparations are in hand as are the SOPs for chondrocytes from a variety of human and animal cartilages; these are also expected to be used by participants and collaborators. Drs. Solchaga (12 years), Caplan (38 years), Lennon (25 years) and Haynesworth (13 years) have over 88 years of combined experience with mesenchymal progenitor cells, chondrocytes and osteoblasts in culture and will provide uniform, reproducible cell preparations for the users of the Core Laboratory.